Hi-Fi Setup

Well, I've finally decided to make the leap to hi-fi, and I've been able to come up with some requirements for the products I wish to buy. Here are all of my requirements listed by component:

DAC:

Must have a frequency response of at least 5 Hz - 30 kHz. The lower bound can be lower and the upper bound can be higher.
Minimal roll-off in bass is preferred.

Must have at least USB and TRS inputs

RCA stereo output is fine, but TRS if not possible (and also preferred).

Output power is not much of an issue considering the amp requirements, but 200 mW is good enough.

Equalizer:

Preferably parametric (that may be the only possibility considering the next requirement).

Must be able to boost ~10 Hz by at least 24 dB.

At least TRS input and output.

Same frequency response requirement as the DAC.

Amp:

Same frequency response as the DAC.

Don't care about bass boost functionality.

At least TRS inputs and outputs.

Output power of at least 300 mW @ 32 ohm (a Big Joe Power Amp if all else fails ).

Headphone:

"A significant upgrade from the Sony MDR-XB700"

Using the XB700 as a base, these headphones should have ("or greater" is implied, as in "similar or greater"):

Similar bass extension.

Greater sound stage.

An open characteristic akin to the SRH440.

Capable of producing significant amount of subsonic bass (kind of an umbrella requirement).

My budget is $2000. In another post, I initially said $500 for the headphones, but that would be half-assed of me. For what I want, I've found the resolve (and the savings) to invest in good audio. The aim of my setup is to reproduce all sound at an audible level with an emphasis on sub-bass. Of course, I don't see any headphone (or speaker, or anything for that matter) that has the driver capability to produce 1 Hz at an audible level, but that's not the aim of my setup. I want the components to get as close to producing those frequencies as possible. I find sub-bass to be less intrusive than mid-bass while also providing greater power to a song than other bass frequencies.

I found the Cambridge Audio DacMagic for $429. Are there any cheaper options? otherwise it is fine. As for the equalizer, the Rane PE 17 is the only one I can find that fits the requirement. In fact, there's an eBay auction for one right now for cheap (it could be broken). I found many more amps than DAC's that fit my requirement, and I haven't really narrowed my choices. Then, the most important component of all, the headphone. I'm looking at the Denon AH-D500, Ultrasone HFI-780, Reloop RHP-20, Ultrasone Proline 650 (really considering it), Shure SRH750DJ (really considering it), and BeyerDynamic DT 770 (is it really much of an upgrade?). What I'm looking for is, in a nutshell, a marriage between (the bass of the XB700 and the open nature and clarity of the SRH440) + bass. So my question to you all is do you have any suggestions as to what products to buy or comments about my requirements?